Speed Cameras on the M4 5385The "speed the road will allow" or even the design maximum speed of a road has nothing to do with the NSL, since most roads were...
It would be good to see some kind of consistent scientific basis to speed limits (you've got to have some kind of limit or the turbo-nutter hooligans will be even less controllable). You can do psychometric tests of a large cross-section of drivers to establish the spread of hazard perception abilities and reaction times. You can test modern cars on modern road surfaces in various weather conditions to review the out-ot-date braking distances quoted in the HC (thinks - why couldn't car manufacturers, or EuroNCAP maybe, develop a standard braking test, and quote *actual* stopping distances?). You can use digital maps to establish sightlines and gradients for every road in the country. Build in other factors - typical traffic densities, weather profiles, housing schools, time of day (variable speed limits - why not!). Work from the starting point that you must be able to stop on any road within the distance you can see to be clear to set the absolute upper limit. So a narrow twisty road gets a lower limit than a wide straight one, and most drivers will understand that. Unlike the random wet-fingered guessing that seems to go on these days, which is why I'm still puzzled why the narrow twisty road near me has a *higher* limit than the equally populated wide straight one!
R
